Expression levels of FUCA-1 in less aggressive thyroid cancers (PTC), in poorly differentiated thyroid carcinomas (PDTC), which represent an histological subtype with intermediate clinical behavior between differentiated and undifferentiated or anaplastic carcinomas, and in highly malignant invasive and metastatic anaplastic thyroid cancers (ATC) were compared with those of normal thyroid tissues (NT). This evidence concerns the gene FUCA1 and thyroid cancer.